After a year spent in middle schools on mini contracts, Marotta, 28, looked forward to having a full-time job working with elementary children — a lifelong dream.

Two months later, she transferred to a job teaching math at Seven Springs Middle School. Requirements to review mountains of data at D-rated Calusa left her little time to prepare and improve lessons, she said.

"I would really love to teach elementary," Marotta said. "But there were just so many extra responsibilities."

Her move highlighted a growing problem in the Pasco school district: Its high-needs schools struggle to retain teachers, in turn hurting efforts to improve academic performance.

Calusa, for example, saw 23 instructional positions change hands between the 2011-12 school year and the current one. That's about half of the teaching staff.

Cox, Gulf Highlands and Lacoochee elementary schools each had 14 teachers and support staff leave. Higher performing schools such as Trinity Oaks and Wesley Chapel have almost no turnover by comparison, assistant superintendent for elementary schools David Scanga said.

"We need to find a way to make it more appealing, more advantageous for teachers to feel rewarded for working in high-needs schools," Scanga said. "The mobility is there, and it's a serious problem."

The issue is on superintendent Kurt Browning's priority list.

"We're not going to make the achievement gains we want if there's a constant turnover," Browning said. "We want to make sure we get the best instructional people in those schools."

School Board member Allen Altman has advocated paying a bonus to teachers who take on the challenge.

"I don't know that we can afford it financially," Altman said. "For the benefit of our students, I don't know that we can afford not to. We need to take a fresh look at it."

Differential pay is one possibility, Browning said. Hillsborough schools offer an example. He said he would also want to make sure that teachers are getting the materials they need, and that proper leadership is provided in the schools.

"It also goes to the workload issues," he said, nodding to a class-action grievance from elementary teachers contending they're too burdened with meetings and tests and data sessions — initiatives that are often magnified in schools struggling to improve outcomes.

"Everything is on the table," Browning said.

Marotta was iffy on the idea of more money.

Her issue was having enough time to spend with her 4-year-old and 8-year-old, who had begun to express surprise when she actually had time to play with them. She was taking home three hours of work a night.

"We needed more support," she said. "Maybe once a month get us a sub and give us a whole day to plan."

Calusa principal Kara Merlin was the first to admit the school's push for improvement takes a toll. The state has reviewers constantly in the school examining teaching methods, the teachers are regularly meeting.

"We do experience more turnover, because it's hard work," she said.

In addition to the 23 positions that changed between school years, Calusa also lost five teachers since August.

It creates stress for the school, which has to find and train new teachers, Merlin said. It also impacts students, who have formed bonds with their teachers only to see them leave. All of this can negatively influence learning.

That knowledge weighed on Marotta.

At first, she considered staying put, having seen her students improve during her short time. One special needs student, making a first attempt at mainstreaming, had done so well that it caused her special pause.

Even after deciding to move, she cried in her car for nearly two hours. But she felt like she had to do it.

She's not alone in the district.

Kara Smucker took over as principal of Gulf Highlands Elementary after it received an F from the state. As she looked at the school's data, Smucker saw that Gulf Highlands already had a teacher turnover rate of more than 20 percent each year.

"It is concerning," she said. "Our children, when they come from homes in poverty, you would want their teacher to be there for them each and every day. You want that consistency. It has been a challenge."

Smucker added hours of professional development to the staff work load, as well as other extra work to get the school back on track. Some teachers asked to leave. New teachers were asked at their interviews to accept the challenge and the time commitment before they were hired.

"If they don't feel that the beliefs and instructional practices are aligned with what they want, I would prefer that they not be here," she said.

She suggested a minimum of a one-year commitment from teachers — more would be preferable — to help keep the school on track. But even that's a difficult request, Smucker and others admitted, because teachers aren't chained to their schools and schools don't necessarily want unhappy employees just waiting to transfer.

Right now, the district offers teachers at Lacoochee a $1,200 annual bonus, recognizing few teachers live in the community so many have to commute. But that hasn't been enough, Scanga said.

"We've got to do better than we've done in the past," he said. "We need to find a way to say we're going to keep some stability in the faculty."

Browning said his new division of student achievement will begin seeking answers once everyone is settled into positions.

"We need to find out what is making them unhappy," he said of the teachers.

Jeffrey S. Solochek can be reached at jsolochek@tampabay.com, (813) 909-4614 or on Twitter @jeffsolochek. For more education news visit the Gradebook at tampabay.com/blogs/gradebook.